1. Field of the Invention
The present invention relates to a ceramic material, laminate, member for use in semiconductor manufacturing equipment, and a sputtering target member.
2. Description of Related Art
In semiconductor manufacturing equipment used for dry processes, plasma coating, and so forth in semiconductor manufacturing, a high-reactive halogen (e.g., F or Cl)-based plasma is used for etching and cleaning. Thus, members used in the semiconductor manufacturing equipment are required to have high corrosion resistance. In general, high-corrosion high-corrosion resistant metals, such as anodized aluminum and hastelloy, and ceramic members are used. In particular, materials for electrostatic chucks and heaters, which support Si wafers, are required to have high corrosion resistance and low particle emission properties. Thus, high-corrosion resistant ceramic members composed of, for example, aluminum nitride, alumina, sapphire, are used. Long-term use of these materials causes them to corrode gradually, so that particles can be emitted. Thus, a higher corrosion resistant material is required. To meet the needs, studies have been conducted on the use of magnesia, spinel (MgAl2O4), composite materials thereof, which have higher corrosion resistance than alumina and so forth (for example, Patent Document 1).
Furthermore, finer lines require members, such as electrostatic chucks and heaters, which support Si wafers, to have excellent temperature uniformity. To improve the temperature uniformity, a material having high thermal conductivity is preferably used. Examples of the material include aluminum nitride, alumina, and yttria. Among these compounds, aluminum nitride has particularly high thermal conductivity and thus can exhibit high temperature uniformity. However, aluminum nitride is known to have low corrosion resistance against a plasma, compared with alumina and yttria.
Furthermore, magnesium oxide is used for refractory materials, various additives, electronic components, fluorescent materials, various target materials, underlying materials for superconducting thin films, tunnel barriers of magnetic tunnel junction devices (MTJ devices), protective films for color plasma displays (PDPs), and used as a raw material for crystalline magnesium oxide layers for PDPs. Thus, magnesium oxide has been attracting attention as a material having a very wide range of applications. In particular, magnesium oxide is used as a sputtering target material to produce tunnel barriers of MTJ devices using the tunneling magnetoresistive effect and protective films for dielectrics and electrodes of PDPs. In a MTJ device including a very thin insulator, which has a thickness of several nanometers, interposed between two magnetic layers, the resistance of the device is different between when relative magnetization directions of the two magnetic layers are parallel to each other and when they are antiparallel to each other. The resistance change phenomenon is referred to as the tunneling magnetoresistive effect. The utilization of the electrical resistance change in the magnetized state enables the device to be applied to, for example, magnetic heads of hard disks.